Fruits, such as citrus fruit and apples, are commercially treated with an aqueous coating of wax composition material or other preservative material to protect the fruit during periods of storage and in transit and to enhance the appearance of the fruit at the marketplace. It is desirable that the surface of the fruit be commercially dry to facilitate handling, packing and shipping. Aqueous coatings applied to fruit are considered to be commercially dry, that is, sufficient water removed, when they are not tacky, portions of the coating are not transferred to other equipment upon contact therewith such as conveyors, and the coating is pliable and does not crack or powder.
Fruit such as apples may be stored at temperatures close to freezing and during application of a protective coating thereto may sweat and become moist from water condensing from the air. Water to be removed by drying includes not only water in the aqueous coating, but also moisture remaining on the apple prior to waxing. Citrus fruit, such as lemons, may be stored at higher temperatures, in the nature of 42.degree.-58.degree. F.; and the water to be removed by drying is essentially that water in the aqueous coating, water left after washing, or water not removed after washing.
Prior proposed fruit drying apparatus have included open type dryers in which a series of fans were positioned above a roll conveyor, alternate fans being equipped with hot water or steam coils for heating air directed downwardly on the fruit. Such an open-type dryer of approximately 6 feet wide and 48 feet long with a conveyor moving at about 10-20 feet per minute was designed to handle 900 cartons per hours or a total of 50,000 lbs. of fruit per hour (55 lbs. per carton). The hot water or steam coils used between 800,000 to 1,000,000 BTU's with a consequent drying time of 21/2 to 3 minutes.
Another prior proposed dryer was designed to handle 1500 cartons per hour or 82,500 lbs. of fruit per hour. This dryer had an area of 280,000 square feet and required 1.2 million BTU's to heat 12,000 CFM with motors of 13 to 15 hp required for moving the air. Drying time in this dryer was approximately 2 to 21/2 minutes. In prior proposed dryer constructions known to me, the fans or blowers used to circulate heated air were arranged above the conveyor means and spaced along the length of the conveyor means. Thus, drying air was blow downwardly and directly against the layer of fruit carried by the conveyor means. The temperature of drying air in such prior proposed apparatuses was often as high as 160.degree. F. to provide suitable drying. Drying air which passed through the layer of fruit and through the conveyor means was discharged to atmosphere.